This invention relates to an apparatus for chilling fluids, particularly but not exclusively canned or bottled beverages. More particularly, the present invention is directed towards a fluid chilling apparatus of the type in which the temperature reduction caused by the desorption of a gas from an adsorbent is used to chill a beverage, such as is disclosed in European patent number 0752564.
In known apparatus for chilling fluids, of the type disclosed in EP0752564, a chilling cartridge is in either direct or indirect thermal contact with the fluid to be chilled (that is, the cartridge is either immersed in the fluid, or forms part of the fluid container, or it is adapted to fit into a recess formed in the container wall, or to fit around the container). The cartridge comprises a sealed thin-walled vessel (the thinness being preferable to promote heat transfer) containing an adsorbent for receiving and adsorbing under pressure a quantity of gas. For example, the adsorbent is activated carbon and the gas is carbon dioxide. On breaking the vessel seal and releasing the pressure, the gas is desorbed, and the endothermic process of desorption of the gas from the adsorbent causes a reduction in the temperature of the adsorbent and of the desorbed gas. Because the cartridge is in thermal contact with the fluid, this reduction in temperature leads to heat transfer from the fluid, through the vessel wall, to the adsorbent and desorbed gas therein, which serves to chill the fluid.
It is known that most adsorbents are poor conductors of thermal energy. For example, activated carbon can be described as an amorphous material, and consequently has a low thermal conductivity even when tightly compacted. This is disadvantageous because poor heat transfer to the adsorbent in the center of the body of adsorbent in the vessel reduces the chilling rate and/or wastes the "chilling power" of the central adsorbent. Accordingly, a number of embodiments of heat transfer means are disclosed in co-pending U.S. patent application Ser. No. 09/002,478 which improve heat transfer between the center of the adsorbent and the vessel walls.
A further problem with conventional arrangements arises from the flow of desorbed gas. In the interest of maximizing the quantity of adsorbed gas in the adsorbent, it is desirable that the adsorbent be highly compacted. However, such compactness reduces the porosity of the body of adsorbent, and so tends to retard the rate of desorption from within the body of the adsorbent, which slows the rate of chilling of the fluid. Secondly, although part of the desorbed gas leaves the adsorbent adjacent the nearest wall, and then travels along the vessel walls to the exit valve, a significant portion also permeates through the adsorbent to the exit valve of the vessel without coming into contact with the vessel walls, and thus a significant amount of "chilling power" (in the desorbed gas lost in this way) is effectively wasted as "sensible heat".